MDF is a lightweight engineered wood product that cuts and works just like wood but with less movement due to changes in humidity and temperature. MDF moulding comes preprimed and ready to paint. Its workability and stability make MDF a good choice for any moulding application where a paint grade solution is desired. The most important tool when working with moulding is patience. Never try to rush trim work. Lowe's is happy to provide this information as a service to you.

Tools and Materials

Tools

• Tape measure    
• Dropcloth
• Drill/driver    
• Dust mask
• Bits    
• Caulk gun
• Hammer    
• Paintbrush or staining brush
• Level    
• Goggles
• Miter saw    
• Nail set

Materials

• Wood putty
• Moulding
• Stain or paint
• Nails
• Caulk      

Locating, Cutting and Fitting

• General

Start by cutting your moulding pieces a little long, you can always trim a little off, but once a piece is too short it can't be fixed.

Predrill holes for nails to avoid splitting the moulding.

If you use a power miter saw, use at least a 60 tooth blade.

In order to establish a level line for a chair rail, measure up from the floor to where the bottom of the chair rail will be and make a mark. Use a level as a straight edge and lightly draw a line around the room. As you install the chair rail, make sure it is even with this line.

• Base and Chair Rail Corners

Lay the moulding with its back flat against the bottom of the miter box or the bed of the power miter saw. For inside corners, cut through the face at 45° so the edge of the cut is visible from the front. For outside corners, cut through the face at 45° so the edge of the cut is hidden from the front. Cut the pieces as mirrors to each other.

• Crown Corners

For outside corners, use a power miter saw and set it as indicated in in our crown moulding adjustment table. For inside corners, you can either miter cut the pieces or cope them.

To miter the pieces, place the moulding so its top (the part that goes against the ceiling) is flat against the bottom of the miter box or bed of the power miter saw. The bottom (the part that goes against the wall) should be flat against the side of the miter box or the power miter saw's fence. Cut the pieces as mirrors to each other on 45° angles.

To cope the pieces, butt one piece tight against the wall and nail in place. Place the second piece in your miter box or power miter saw as described above and cut the piece at 45° so the edge of the cut is visible from the front. Use a coping saw to cut a slight back angle following the contour of the exposed moulding profile. Test fit the coped cut and trim as necessary. See the animation below for more information on coping moulding.

• Splicing All Types of Moulding

When you are covering a span that is longer than your moulding, splice two pieces together with a scarf joint. Lay the moulding with its back flat against the bottom of the miter box or the bed of the power miter saw. On one piece, cut through the face at 45° so the edge of the cut is visible from the front. On the second piece, cut through the face at 45° so the edge of the cut is hidden from the front. The joint should meet over a wall stud or some other point where it can be nailed.

Using Corner Blocks

To make installing MDF moulding even easier, there are corner blocks and divider blocks. These blocks eliminate the need to cope, miter or splice when installing your moulding. Installing MDF moulding using corner blocks is very similar to installing decorative hardwood moulding using corner blocks.

Determine How Much Moulding You Need

1. Measure the room at the height where each moulding will go to determine the number and the length of the pieces you'll need. Jot these measurements down.
2. Since MDF moulding usually comes in 8' lengths, divide your footage by eight and multiply that number by 1.1. The result is the total footage needed plus ten percent for waste. Perform this step for each type of moulding, base, chair rail and crown, separately.

Apply the Finish
 

1. Apply the finish to the moulding before installing it. You'll save time because you can apply the finish faster. Find a dry, well-ventilated and dust-free area to apply the finish to your moulding.
2. Put down a dropcloth and apply the finish according to the manufacturers' instructions. Apply the finish to the moulding in the same order you intend to install the pieces. Then you won't have to spend as much time waiting for pieces to dry.
3. Set aside some finish to touch up any raw edges.

Install the Moulding

1. Locate and lightly mark the wall studs (see How to Find Studs in Finished Walls).
2.  Measure the distance between two inside corners and cut a piece of moulding to fit between the corners. Predrill the moulding at every wall stud and nail in place. To avoid denting the moulding, use a nail set to finish driving the nails home. You may need someone to help hold long pieces while you drill and nail. In the event you have a span between two corners longer than the moulding, simply make a scarf joint as mentioned above to splice two pieces.
3. Continue installing pieces until all the moulding is up.
4. After all the moulding is up, touch up any raw edges with a light coat of finish. Use wood putty or a filler stick to hide nail holes. For crown moulding, it may be necessary to apply a bead of caulk where the moulding meets the ceiling to close any gaps.